why will the country name not be declined
here US is a subject, so it is in Nominative.
Should it not be jest instead of są?
could it not better be, where are the United States?
Both are accepted, the is/are question is problematic, but as far as I know, "is" should technically be the correct option when talking about the country.
No, "Stany Zjednoczone" are definitely and logically plural in Polish.
The abbreviation USA (U-ES-A) is more problematic, but it also should be considered plural.
but why do the americans say is the United States? it is not only one State there are some
As far as I understand: "United States" is a country. There are 50 states in this country.
Precisely. You might find this interesting. :)
States are plural, so... są... one state is... jest...
The United States is a single country, so "is" is the appropriate word.